Dust cloths for removing dust from a surface to be cleaned, such as a table, are generally known. Such known dust cloths may be made of woven or nonwoven fabrics and are often sprayed or coated with a wet, oily substance for retaining the dust. However, such known dust cloths tend to leave an oily film on the surface after use.
Other dust cloths utilize composites of fibers bonded together via adhesive, melt bonding, entanglement or other forces. To provide durable cloths, the staple fibers can be combined with some type of reinforcement, such as a continuous filament or network structure. Other cloths have attained the desired durability by employing fibers which are strongly bonded together, e.g., via adhesive bonding or melt bonding. While having good durability, such cloths may be less effective in their ability to pick up and retain particulates like dust and dirt.
Other known dust cloths include nonwoven entangled fibers having spaces between the entangled fibers for retaining the dust. The entangled fibers may be supported by a network grid or scrim structure, which can provide additional strength to such cloths. Cloths of this type can become saturated with the dust during use (i.e., dust buildup) and/or may not be completely effective at picking up denser particles, large particles or other debris.
Accordingly, it would be advantageous to provide cleaning sheets that can pick-up and retain debris. Such a cleaning sheet would preferably be capable of retaining relatively large and/or denser particles of debris while at the same time being very effective for picking up and retaining fine dust particles.
The present invention relates generally to cleaning sheets for use in cleaning surfaces, e.g., in the home or work environment. More particularly, the invention relates to a cleaning sheet for collecting and retaining dust, larger particles and/or other debris. The cleaning sheet includes a surface covered with a fabric material capable of picking up and retaining particulate matter and other debris, such as hair and lint. The outer surface of the fabric material includes a plurality of cavities therein. The cavities are typically larger relative to the particulate matter the cleaning sheets are designed to retain, e.g., commonly having a cross-sectional area of at least 3-4 mm2. The fabric material may optionally be treated with and/or incorporate therein a dust adhesion agent to enhance its effectiveness.
The cleaning sheet can include a fabric layer secured to a flexible backing layer so as to define an outer fabric surface with a plurality of cavities therein. The cavities commonly include a tacky surface. The cleaning sheet may include adhesive disposed between the fabric layer and the flexible backing layer. In such an embodiment, the fabric layer can have a plurality of apertures therethrough which expose at least a portion of the adhesive thereby forming cavities which have a tacky bottom surface. The present cleaning sheets generally have a breaking strength of at least 500 g/30 mm and an elongation at a load of 500 g/30 mm of no more than about 25%.
In another embodiment, the cleaning sheet has a first surface including a nonwoven fiber aggregate layer. A flexible backing layer is secured to the nonwoven fiber aggregate layer. The first surface has a plurality of cavities therein, which include a tacky surface capable of retaining particles, such as dust and dirt. The nonwoven fiber aggregate layer may be secured to the flexible backing layer by an intervening adhesive layer, e.g., a layer of pressure sensitive adhesive. A suitable nonwoven fiber aggregate layer is formed from a loosely entangled fibrous web which has a plurality of apertures therethrough. Such a fibrous web typically has a basis weight of 30 to 100 g/m2 and a CD initial modulus (xe2x80x9centanglement coefficientxe2x80x9d) of no more than 800 m.
As used herein, the term xe2x80x9centanglement coefficientxe2x80x9d refers to the initial gradient of the stress-strain curve measured with respect to the direction perpendicular to the fiber orientation in the fiber aggregate (cross machine direction). The entanglement coefficient is also referred to herein as the xe2x80x9cCD initial modulus.xe2x80x9d Suitable nonwoven fiber aggregates for use in forming the present cleaning sheets have an entanglement coefficient of 20 to 500 m (as measured after any reinforcing filaments or network has been removed from the nonwoven fibrous web) and, more typically, no more than about 250 m.
Cleaning sheets according to one embodiment can be produced by coating an adhesive layer onto at least one surface of a flexible backing layer. A fabric layer, such as a nonwoven fiber aggregate layer having a plurality of apertures therethrough, can then be secured onto the coating of the adhesive. Alternatively, a composite material having a surface covered with a fabric layer with a plurality of cavities therein can have adhesive selectively applied to a surface within the cavities, e.g., by spraying a solution or dispersion of a pressure sensitive adhesive onto the bottom surface of the cavities. The fabric layer can be secured to a flexible backing layer by any of a number of conventional methods, e.g., via point melt bonding, adhesive bonding or stitching.
The entanglement coefficient (also referred to herein as xe2x80x9cCD initial modulusxe2x80x9d) as used herein is a measure representing the degree of entanglement of fibers in the fiber aggregate. The entanglement coefficient is expressed by the initial gradient of the stress-strain curve measured with respect to the direction perpendicular to the fiber orientation in the nonwoven fiber aggregate, i.e., in the cross machine direction (xe2x80x9ccross directionxe2x80x9d or xe2x80x9cCDxe2x80x9d). A smaller value of the entanglement coefficient represents a smaller degree of entanglement of the fibers. The term xe2x80x9cstressxe2x80x9d as used herein means a value which is obtained by dividing the tensile load value by the chucking width (i.e. the width of the test strip during the measurement of the tensile strength) and the basis weight of the nonwoven fiber aggregate. The term xe2x80x9cstrainxe2x80x9d as used herein is a measure of the elongation of the cleaning sheet material.
The term xe2x80x9cbreaking strengthxe2x80x9d as used herein refers to the value of a load (i.e. the first peak value during the measurement of the tensile strength) at which the cleaning sheet begins to break when a tensile load is applied to the cleaning sheet.
As used herein, the term xe2x80x9celongationxe2x80x9d refers to the relative increase in length (in percent) of a 30 mm strip of cleaning sheet material when a tensile load of 500 g is applied to the strip. The strip is elongated at a rate of 30 mm/min in the direction perpendicular to the fiber orientation (i.e, in the cross machine direction). As used herein the term xe2x80x9cnonwoven fabric or webxe2x80x9d means a web having a structure of individual fibers or threads which are interlaid, but not in a regular or identifiable manner as in a knitted fabric. The term also includes individual filaments and strands, yarns or tows as well as foams and films that have been fibrillated, apertured, or otherwise treated to impart fabric-like properties. Nonwoven fabrics or webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (xe2x80x9cosyxe2x80x9d) or grams per square meter (xe2x80x9cgsmxe2x80x9d). Fiber diameters useful are usually expressed in microns. Basis weights can be converted from osy to gsm simply by multiplying the value in osy by 33.91.
As used herein the term xe2x80x9cmicrofibersxe2x80x9d means small diameter fibers having an average diameter not greater than about 75 microns, for example, having an average diameter of from about 0.5 microns to about 50 microns, or more particularly, microfibers may have an average diameter of from about 2 microns to about 40 microns. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9000 meters of a fiber and may be calculated as fiber diameter in microns squared, multiplied by the density in grams/cc, multiplied by 0.00707. For example, the diameter of a polypropylene fiber given as 15 microns may be converted to denier by squaring the diameter, multiplying the result by 0.89 g/cc and multiplying by 0.00707. Thus, a 15 micron polypropylene fiber has a denier of about 1.42 (152xc3x970.89xc3x970.00707=1.415). A lower denier indicates a finer fiber and a higher denier indicates a thicker or heavier fiber. Outside the United States the unit of measurement is more commonly the xe2x80x9ctexxe2x80x9d, which is defined as the grams per kilometer of fiber. Tex may be calculated as denier/9.
As used herein, the term xe2x80x9caverage cross-sectional dimensionxe2x80x9d refers to the average dimension of a cavity in an outer fabric surface of the present cleaning sheet. The xe2x80x9caverage cross-sectional dimensionxe2x80x9d (xe2x80x9cACSDxe2x80x9d) is equal to one half of the sum of the length of the longest cross sectional axis (xe2x80x9cLlxe2x80x9d) of the cavity plus the cross sectional axis perpendicular to the longest cross sectional axis (xe2x80x9cLsxe2x80x9d), i.e.,
ACSD=(Ll+Ls)/2.
The term xe2x80x9ccross-sectional areaxe2x80x9d is used herein to refer to the area of a cavity in the outer plane of the fabric surface (i.e., in the cleaning surface). Most cavities will not have sides which are perpendicular to this plane and, thus, the cross-sectional area of a cavity is often larger than the area encompassed by the bottom of the cavity. Where the term xe2x80x9ccross-sectional areaxe2x80x9d is used in reference to a perforation (hole) through the fabric layer, it likewise refers to the area of the perforation at the outer plane of the fabric surface.
It is important to note that the terms xe2x80x9csurfacexe2x80x9d and xe2x80x9csurface to be cleanedxe2x80x9d as used in this disclosure are broad terms and are not intended as terms of limitation. The term surface includes substantially hard or rigid surfaces (e.g., articles of furniture, tables, shelving, floors, ceilings, hard furnishings, household appliances, and the like), as well as relatively softer or semi-rigid surfaces (e.g., rugs, carpets, soft furnishings, linens, clothing, and the like).
It is also important to note that the term xe2x80x9cdebrisxe2x80x9d is a broad term and is not intended as a term of limitation. In addition to dust and other fine particulate matter, the term debris includes relatively large-sized particulate material, e.g., having an average diameter greater than about 1 mm, such as large-sized dirt, soil, lint, and waste pieces of fibers and hair, which may not be collected with conventional dust rags, as well as dust and other fine dirt particles.
Throughout this application, the text refers to various embodiments of the cleaning sheet. The various embodiments described are meant to provide a variety illustrative examples and should not be construed as descriptions of alternative species. Rather it should be noted that the descriptions of various embodiments provided herein may be of overlapping scope. The embodiments discussed herein are merely illustrative and are not meant to limit the scope of the present invention.